Combination padlocks are used in a variety of applications, including, for example, with enclosures such as lockers, storage sheds, and various gates and doors. The locking mechanism of a conventional single dial combination lock 1 is illustrated in FIG. 1. A numbered combination dial 2, which serves as the user interface, is positioned on an external surface of the lock 1. Rotation of the dial causes a drive cam 3 to engage a series of rotating cams 4a, 4b, 4c (usually three for a conventional combination padlock or school locker), each having an outer periphery which holds a latch or fence 7 in a locking condition. Detents 9 extending from each of the cams 4a, 4b, 4c engage each other to cause the cams 4a, 4b, 4c to rotate together. When the dial 2 is rotated to a first desired rotational position and then rotated in an opposite direction (for example, the counterclockwise direction), the first cam 4a remains in a desired rotational position due to separation from the detent 9 of the second cam 4b. When the dial is then rotated to a second desired rotational position and then rotated in an opposite direction (for example the clockwise direction), the second cam 4b remains in a desired rotational position due to separation from the detent 9 of the third cam 4c. When the dial 2 is then rotated to a third desired rotational position, the third cam 4c is positioned accordingly. In this fashion, the dial 2 may be rotated to successive desired positions (identified by the numbers on the dial 2) that align notches 6 in each of the cams 4a, 4b, 4c with the fence 7. When all of the notches 6 are aligned with the fence 7, the fence may be permitted to move into the aligned notches 6 (for example, by user movement or by a spring loaded mechanism), allowing a locking member 5 to move out of locking engagement with a locked obstruction, such as, for example, a shackle, in the case of a combination padlock, or a locker door, in the case of a combination locker lock.
While the use of a combination lock, as compared to a key based lock, may eliminate the risk of lost, stolen, or copied keys, an authorized combination may still be learned by an unauthorized user, or known by a once-authorized user to whom access is no longer desired. In these and other circumstances, an authorized user may wish to change the unlocking combination.
A conventional combination padlock is maintained in a locked condition by a latch that engages one leg of a shackle. Such a lock may be susceptible to tampering by rapping or shimming the latch out of engagement with the shackle to open the lock. As another characteristic of a conventional combination padlock, the internal cams rotated to an authorized combination to open the lock may remain at or near this authorized combination upon re-locking the lock, thereby potentially compromising lock security. As still another characteristic of a conventional combination padlock, the combination dial is controlled by a relatively small knob that may be ergonomically difficult to manipulate. Further, when dialing the combination on a conventional combination padlock, rapid revolution of the numbers on the dial may cause the numbers to visually wash together, making it difficult to accurately rotate the dial to the proper position without slowing rotation of the dial in order to view the numbers.